CN110419169B

CN110419169B - Method for applying resource bundling-based precoder in wireless communication system and apparatus therefor

Info

Publication number: CN110419169B
Application number: CN201880018489.1A
Authority: CN
Inventors: 金亨泰; 姜智源; 金沂濬; 朴钟贤; 朴海旭
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2017-03-17
Filing date: 2018-03-19
Publication date: 2021-11-26
Anticipated expiration: 2038-03-19
Also published as: EP3598658A1; US11032046B2; EP3598658A4; JP6898997B2; JP2020512731A; US20200099488A1; CN110419169A; EP3598658B1; WO2018169375A1

Abstract

A method of transmitting an uplink signal by a terminal in a wireless communication system is disclosed. The method comprises the following steps: transmitting, to a base station, a plurality of precoding reference signals each to which a precoder cycling pattern is applied in a predetermined resource unit; receiving information indicating one of a plurality of precoded reference signals from a base station; and transmitting the uplink data signal and the uplink demodulation reference signal to the base station by using the precoder cycling pattern that has been applied to the indicated precoding reference signal.

Description

Method for applying resource bundling-based precoder in wireless communication system and apparatus therefor

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a method of applying a resource bundling-based precoder in a wireless communication system and an apparatus therefor.

Background

As an example of a wireless communication system to which the present invention is applicable, a 3GPP LTE (third generation partnership project long term evolution, hereinafter abbreviated LTE) communication system is schematically explained.

Fig. 1 is a schematic diagram of an E-UMTS network structure as one example of a wireless communication system. The E-UMTS (evolved universal mobile telecommunications system) is a system evolved from the conventional UMTS (universal mobile telecommunications system). Currently, 3GPP is performing basic standardization work for E-UMTS. E-UMTS is commonly referred to as an LTE system. For details of the technical specifications of UMTS and E-UMTS, see "3 rd generation partnership project; technical specification group radio access network "(" third generation partnership project "; technical specification group radio access network") release 7 and release 8.

Referring to fig. 1, the E-UMTS includes a User Equipment (UE), an eNode B (eNB), and an access gateway (hereinafter, abbreviated AG) connected to an external network in such a manner as to be located at an end of a network (E-UTRAN). The eNode B is capable of simultaneously transmitting a plurality of data streams for a broadcast service, a multicast service, and/or a unicast service.

One eNode B includes at least one cell. The cell provides a downlink transmission service or an uplink transmission service to a plurality of user equipments by being set to one of bandwidths of 1.25MHz, 2.5MHz, 5MHz, 10MHz, 15MHz, and 20 MHz. Different cells may be configured to provide respective bandwidths. The eNode B controls data transmission/reception to a plurality of user equipments. For downlink (hereinafter, abbreviated as DL) data, the eNode B notifies a corresponding user equipment of time/frequency region, coding, data size, HARQ (hybrid automatic repeat and request) related information, etc. of transmitting data by transmitting DL scheduling information. Also, for uplink (hereinafter abbreviated UL) data, the eNode B informs the respective user equipments of a time/frequency region, coding, data size, HARQ-related information, etc., which can be used by the respective user equipments, by transmitting UL scheduling information to the respective user equipments. An interface for user traffic transmission or control traffic transmission may be used between eNode bs. The Core Network (CN) is composed of a network node and an AG (access gateway) for user registration of user equipment and the like. The AG manages mobility of the user equipment in units of TAs (tracking areas) composed of a plurality of cells.

Wireless communication technologies have evolved to LTE based on WCDMA. However, the continuing demand and desire of users and service providers continues to increase. In addition, as different kinds of radio access technologies are continuously developed, new technological evolution is required to have competitiveness in the future. Future competitiveness requires a reduction in cost per bit, an increase in service availability, flexible band use, a simple structure/open interface, reasonable power consumption of user equipment, and the like.

Disclosure of Invention

[ problem ] to

Based on the above discussion, the present invention provides a method and apparatus for applying a resource bundling-based precoder in a wireless communication system.

Objects that may be achieved by the present invention are not limited to what has been particularly described hereinabove, and other objects not described herein will be more clearly understood by those skilled in the art from the following detailed description.

[ solution ]

According to an aspect of the present invention, there is provided a method of transmitting an uplink signal by a User Equipment (UE) in a wireless communication system, including: transmitting a plurality of precoding reference signals to which a precoder cycling pattern is applied in a predetermined resource unit to a Base Station (BS); receiving information indicating one of a plurality of precoded reference signals from a BS; and transmitting the uplink data signal and the uplink demodulation reference signal to the BS using the precoder cycling pattern applied to the indicated precoding reference signal.

In another aspect of the present invention, there is provided a User Equipment (UE) in a wireless communication system, comprising: a wireless communication module; and a processor connected to the wireless communication module and configured to transmit a plurality of precoding reference signals to which a precoder cycling pattern is applied in a predetermined resource unit to a Base Station (BS), receive information indicating one of the plurality of precoding reference signals from the BS; and transmitting the uplink data signal and the uplink demodulation reference signal to the BS using the precoder cycling pattern applied to the indicated precoding reference signal.

The precoder cycling pattern applied to the plurality of precoded reference signals may be defined as a combination of a first precoder for each of the plurality of precoded reference signals and a second precoder applied in common to the plurality of precoded reference signals and cyclically applied in predetermined resource units.

The UE may determine a first precoder for each of a plurality of precoded reference signals using a downlink reference signal received from the BS.

The precoder cycling pattern applied to the plurality of precoded reference signals may precode the precoded reference signals in different directions in the horizontal domain, and may be defined to cover all horizontal directions.

The UE may receive information on the predetermined resource unit from the BS.

[ advantageous effects ]

According to embodiments of the present invention, a resource bundling-based precoder may be efficiently applied in a wireless communication system, in particular, in uplink reference signal transmission.

It will be appreciated by those skilled in the art that the effects that can be achieved by the present invention are not limited to what has been particularly described hereinabove, and other advantages of the present invention will be more clearly understood from the following detailed description.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

Fig. 1 is a diagram schematically showing a network structure of E-UMTS as an exemplary radio communication system.

Fig. 2 is a diagram illustrating the structure of a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network specification.

Fig. 3 is a diagram illustrating a physical channel used in a 3GPP system and a general signal transmission method using the physical channel.

Fig. 4 is a diagram illustrating a structure of a radio frame used in the LTE system.

Fig. 5 is a diagram illustrating a structure of a DL radio frame used in the LTE system.

Fig. 6 is a diagram illustrating a structure of a UL subframe in an LTE system.

Fig. 7 is a diagram showing a configuration of a general MIMO communication system.

Fig. 8 is a flowchart illustrating a communication method using UL precoded SRS according to an embodiment of the present invention.

Fig. 9 is a schematic diagram illustrating a BS and a UE suitable for an embodiment of the present invention.

Detailed Description

The configuration, operation, and other features of the present invention will be understood by the embodiments of the present invention described with reference to the accompanying drawings. The following embodiments are examples in which technical features of the present invention are applied to a third generation partnership project (3GPP) system.

Although the embodiments of the present invention will be described based on the LTE system and the LTE-advanced (LTE-a) system, the LTE system and the LTE-a system are only exemplary, and the embodiments of the present invention can be applied to any communication system corresponding to the aforementioned definition. Furthermore, although embodiments of the present invention are described herein with reference to an FDD system, this is merely exemplary. Also, the embodiments of the present invention can be applied to an H-FDD or TDD system by being easily modified.

Fig. 2 is a diagram illustrating the structure of a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network specification. The control plane refers to a path for transmitting a control message, which is used by the UE and the network to manage a call. The user plane refers to a path for transmitting data (e.g., voice data or internet packet data) generated in an application layer.

The physical layer of the first layer provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to a Medium Access Control (MAC) layer of an upper layer via a transport channel. Data is transferred between the MAC layer and the physical layer via a transport channel. Data is also transmitted between the physical layer of the transmitter and the physical layer of the receiver via a physical channel. The physical channel uses time and frequency as radio resources. Specifically, the physical channel is modulated using an Orthogonal Frequency Division Multiple Access (OFDMA) scheme in the DL, and is modulated using a single carrier frequency division multiple access (SC-FDMA) scheme in the UL.

The MAC layer of the second layer provides a service to a Radio Link Control (RLC) layer of an upper layer via a logical channel. The RLC layer of the second layer supports reliable data transmission. The function of the RLC layer may be implemented by a function block within the MAC layer.

A Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function to reduce unnecessary control information, thereby efficiently transmitting Internet Protocol (IP) packets such as IPv4 or IPv6 packets in a radio interface having a narrower bandwidth.

A Radio Resource Control (RRC) layer located at the bottommost of the third layer is defined only in the control plane. The RRC layer controls logical channels, transport channels, and physical channels related to configuration, reconfiguration, and release of radio bearers. The radio bearer refers to a service provided by the second layer for transmitting data between the UE and the network. To this end, the RRC layer of the UE and the RRC layer of the network exchange RRC messages. The UE is in an RRC connected mode if an RRC connection has been established between the RRC layer of the radio network and the RRC layer of the UE. Otherwise, the UE is in RRC idle mode. A non-access stratum (NAS) layer located at an upper layer of the RRC layer performs functions such as session management and mobility management.

The cell constituting the eNB is configured by one of bandwidths among 1.25MHz, 2.5MHz, 5MHz, 10MHz, 15MHz, and 20MHz, and provides a DL or UL transmission service to a plurality of UEs. Cells that are different from each other may be configured to provide different bandwidths.

DL transport channels for data transmission from the network to the UE include a Broadcast Channel (BCH) for transmitting system information, a Paging Channel (PCH) for transmitting a paging message, and a DL Shared Channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of the DL multicast or broadcast service may be transmitted through the DL SCH or may be transmitted through an additional DL Multicast Channel (MCH). In addition, UL transport channels for data transmission from the UE to the network include a Random Access Channel (RACH) for transmitting an initial control message and an UL SCH for transmitting user traffic or a control message. Logical channels located at an upper layer of the transport channel and mapped to the transport channel include a Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), a Common Control Channel (CCCH), a Multicast Control Channel (MCCH), and a Multicast Traffic Channel (MTCH).

When power is turned on or the UE enters a new cell, the UE performs an initial cell search procedure, for example, to acquire synchronization with the eNB (S301). To this end, the UE may adjust synchronization with the eNB by receiving a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the eNB, and acquire information such as a cell Identification (ID). Thereafter, the UE may acquire broadcast information within the cell by receiving a physical broadcast channel from the eNB. In the initial cell search procedure, the UE may monitor a downlink reference signal (DL RS) channel state by receiving the DL RS.

After the initial cell search procedure is completed, the UE may acquire more detailed system information by receiving a Physical Downlink Control Channel (PDCCH) and receiving a Physical Downlink Shared Channel (PDSCH) based on information carried on the PDCCH (S302).

Further, if the UE initially accesses the eNB, or if there is no radio resource for signal transmission to the eNB, the UE may perform a random access procedure with the eNB (S303 to S306). To this end, the UE may transmit a specific sequence as a preamble through a Physical Random Access Channel (PRACH) (S303 and S305), and receive a response message to the preamble through the PDCCH and the PDSCH associated with the PDCCH (S304 and S306). In case of the contention-based random access procedure, the UE may additionally perform a contention resolution procedure.

After performing the above-described procedure, the UE may receive the PDCCH/PDSCH (S307) and transmit a Physical Uplink Shared Channel (PUSCH)/Physical Uplink Control Channel (PUCCH) (S308) as a general UL/DL signal transmission procedure. In particular, the UE receives Downlink Control Information (DCI) through the PDCCH. The DCI includes control information such as resource allocation information for the UE and has different formats according to its use purpose.

Also, the control information transmitted by the UE to the eNB on the UL or received from the eNB on the DL includes DL/UL acknowledgement/negative acknowledgement (ACK/NACK) signals, Channel Quality Indicators (CQIs), Precoding Matrix Indexes (PMIs), Rank Indicators (RIs), and the like. In the 3GPP LTE system, the UE may transmit control information such as CQI/PMI/RI through PUSCH and/or PUCCH.

Referring to fig. 4, a radio frame has a length of 10ms (327200 × Ts) and includes 10 equally-sized subframes. Each subframe has a length of 1ms and includes two slots. Each slot has a length of 0.5ms (15360 Ts). In this case, Ts denotes a symbol represented by Ts ═ l/(15kHz x 2048) ═ 3.2552x10^-8(about 33ns) the sample time. Each slot includes a plurality of OFDM symbols in the time domain and includes a plurality of Resource Blocks (RBs) in the frequency domain. In the LTE system, one RB includes 12 subcarriers × 7 (or 6) OFDM symbols. A Transmission Time Interval (TTI), which is a unit time of data transmission, may be determined in units of one or more subframes. The above-described structure of the radio frame is only exemplary, and various modifications may be made to the number of subframes included in the radio frame, the number of slots included in the subframe, or the number of OFDM symbols included in the slot.

Fig. 5 is a diagram illustrating a control channel included in a control region of one subframe in a DL radio frame.

Referring to fig. 5, one subframe includes 14 OFDM symbols. According to the subframe configuration, first to third OFDM symbols among 14 OFDM symbols may be used as a control region, and the remaining 11 to 13 OFDM symbols may be used as a data region. In fig. 5, R0 to R3 represent Reference Signals (RSs) or pilot signals of antennas 0 to 3, respectively. The RS is fixed to a predetermined pattern within a subframe regardless of the control region and the data region. The control channel is allocated to resources not used for the RS in the control region. The traffic channel is allocated to resources not used for the RS in the data region. The control channels allocated to the control region include a Physical Control Format Indicator Channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a Physical Downlink Control Channel (PDCCH), and the like.

The physical control format indicator channel PCFICH informs the UE of the number of OFDM symbols used for PDCCH in each subframe. The PCFICH is located in the first OFDM symbol and is configured with a higher priority than the PHICH and PDCCH. The PCFICH is composed of 4 Resource Element Groups (REGs), and each REG is distributed over the control region based on the cell ID. One REG includes 4 Resource Elements (REs). The RE indication is defined as the minimum physical resource of one OFDM symbol by one subcarrier. The PCFICH value indicates a value of 1 to 3 or a value of 2 to 4 according to a bandwidth, and is modulated using Quadrature Phase Shift Keying (QPSK).

The physical hybrid ARQ indicator channel PHICH is used to carry HARQ ACK/NACK signals for UL transmission. That is, the PHICH indicates a channel through which DL ACK/NACK information for UL HARQ is transmitted. The PHICH includes one REG and is cell-specifically scrambled. The ACK/NACK signal is indicated by 1 bit and is modulated using Binary Phase Shift Keying (BPSK). The modulated ACK/NACK signal is spread with a Spreading Factor (SF) of 2 or 4. A plurality of PHICHs mapped to the same resource constitute a PHICH group. The number of PHICHs multiplexed to the PHICH group is determined according to the number of spreading codes. PHICH (group) is repeated three times to obtain diversity gain in frequency domain and/or time domain.

The PDCCH is allocated to the first n OFDM symbols of the subframe. In this case, n is an integer equal to or greater than 1 indicated by the PCFICH. The PDCCH consists of one or more Control Channel Elements (CCEs). The PDCCH notifies each UE or UE group of information associated with resource allocation of a transport channel, i.e., a Paging Channel (PCH) and a downlink shared channel (DL-SCH), an UL scheduling grant, HARQ information, and the like. The PCH and DL-SCH are transmitted through the PDSCH. Therefore, the eNB and the UE transmit and receive data (except for specific control information or service data) through the PDSCH.

Information indicating to which UE or UEs PDSCH data is to be transmitted and information indicating how the UE should receive and decode PDSCH data is transmitted on the PDCCH. For example, assuming that a Cyclic Redundancy Check (CRC) of a specific PDCCH is masked with a Radio Network Temporary Identity (RNTI) "a" and information on data transmitted using a radio resource "B" (e.g., frequency location) and using a DCI format "C", i.e., transport format information (e.g., transport block size, modulation scheme, coding information, etc.) is transmitted in a specific subframe, a UE located in a cell monitors the PDCCH using its RNTI information in a search space, i.e., blind decodes the PDCCH. If there are one or more UEs having RNTI "a", the UE receives a PDCCH and receives a PDSCH indicated by "B" and "C" based on information of the received PDCCH.

Fig. 6 is a diagram illustrating a structure of a UL subframe in an LTE system.

Referring to fig. 6, an uplink subframe is divided into a region to which a PUCCH is allocated to transmit control information and a region to which a PUSCH is allocated to transmit user data. The PUSCH is allocated to the middle of a subframe, and the PUSCH is allocated to both ends of a data region in the frequency domain. The control information transmitted on the PUCCH includes ACK/NACK, a Channel Quality Indicator (CQI) indicating a downlink channel state, RI for Multiple Input Multiple Output (MIMO), a Scheduling Request (SR) indicating a request for allocation of UL resources, and the like. The PUCCH of the UE uses one RB occupying a different frequency in each slot of the subframe. That is, two RBs allocated to the PUCCH are frequency hopped on a slot boundary. In particular, PUCCHs with m-0, m-1, m-2, and m-3 are allocated to the subframes in fig. 6.

Also, a time at which a Sounding Reference Signal (SRS) may be transmitted in one subframe is a duration during which a symbol located at the last part in one subframe in the time domain exists and the SRS is transmitted through a data transmission band in the frequency domain. According to the frequency location, SRS of a plurality of UEs transmitted on the last symbol in the same subframe can be distinguished.

Hereinafter, a MIMO system will be described. MIMO refers to a method of improving data transmission/reception efficiency using a plurality of transmission antennas and a plurality of reception antennas. That is, a plurality of antennas are used at a transmitting end or a receiving end of the wireless communication system, so that capacity can be increased and performance can be improved. In this disclosure, MIMO may also be referred to as "multiple antennas".

MIMO technology does not rely on a single antenna path to receive the entire message. In contrast, MIMO technology collects data segments received via several antennas, combines the data segments, and forms complete data. The use of MIMO technology can increase the system coverage while increasing the data transmission rate within a cell area of a specific size or guaranteeing a specific data transmission rate. The MIMO technology can be widely used for mobile communication terminals and relay nodes. The MIMO technology can overcome the limitation of the limited amount of transmission data of the mobile communication system based on a single antenna.

Fig. 7 shows a configuration of a general MIMO communication system.

The transmitting end is equipped with NT transmit (Tx) antennas, and the receiving end is equipped with NR receive (Rx) antennas. If a plurality of antennas are used at both the transmitting end and the receiving end, theoretical channel transmission capacity increases, unlike the case where only the transmitting end or the receiving end uses a plurality of antennas. The channel transmission capacity increases in proportion to the number of antennas, thereby improving transmission rate and frequency efficiency. If the maximum transmission rate using a single antenna is Ro, the transmission rate using multiple antennas can theoretically be increased by the product of the maximum transmission rate Ro and the rate increment Ri. The rate increment Ri is represented by the following equation 1, where Ri is the smaller of NT and NR.

[ equation 1]

R_i＝min(N_T,N_R)

For example, in a MIMO communication system using four Tx antennas and four Rx antennas, a transmission rate four times that of a single antenna system can be theoretically obtained. After the theoretical increase in capacity of the MIMO system was first demonstrated in the mid 90 s of the 20 th century, various techniques for greatly increasing the data transmission rate have been under development. Several of these technologies have been incorporated into various wireless communication standards including, for example, third generation mobile communications and next generation wireless local area networks.

Active research related to MIMO technology so far has focused on many different aspects including research on information theory related to MIMO communication capacity calculation in various channel environments and multiple access environments, research on wireless channel measurement and model derivation of MIMO systems, and research on space-time signal processing techniques for improving transmission reliability and transmission rate.

In order to describe the communication method in the MIMO system in detail, a mathematical model thereof is given below. As shown in fig. 7, it is assumed that NT Tx antennas and NR Rx antennas exist. In case of transmitting a signal, the maximum number of pieces of transmittable information in case of using NT Tx antennas is NT, so that the transmitted information can be represented by a vector represented by the following equation 2:

[ equation 2]

In addition, each piece of transmission information S₁,S₂，…，

May have different transmit powers. In this case, if each transmission power is represented by P₁，P₂，…，

Expressed, the transmission information having the adjusted transmission power may be represented by a vector shown in the following equation 3:

[ equation 3]

Transmission power controlled transmission information vector

The diagonal matrix P of transmit powers can be expressed as follows:

[ equation 4]

NT transmission signals x to be actually transmitted₁，x₂，…，

Information vector capable of controlling transmission power

Multiplied by a weight matrix W. In this case, the weight matrix is adapted to appropriately allocate transmission information to the respective antennas according to the transmission channel situation. Transmitting signal x₁，x₂，…，

The vector X can be represented by the following equation 5. In equation 5, W_ijIs a weight between the ith Tx antenna and the jth information, and W is a weight matrix, which may also be referred to as a precoding matrix.

[ equation 5]

In general, the physical meaning of the rank of a channel matrix may be the maximum number of different pieces of information that can be sent in a given channel. Therefore, since the rank of the channel matrix is defined as the smaller one of the number of rows or columns independent of each other, the rank of the matrix is not greater than the number of rows or columns. The rank of the channel matrix H, i.e. the rank (H), is limited as follows.

[ equation 6]

rank(H)≤min(N_T，N_R)

Each unit of different information transmitted using MIMO technology is defined as a "transmission stream" or simply a "stream". The "stream" may be referred to as a "layer". The number of transmission streams is not greater than the rank of the channel which is the maximum number of different transmittable information. Accordingly, the channel matrix H can be represented by the following equation 7:

[ equation 7]

#of streams≤rank(H)≤min(N_T，N_R)

Wherein "# of streams" indicates the number of streams. It should be noted that one stream may be transmitted through one or more antennas.

There may be various ways to allow one or more streams to correspond to multiple antennas. These methods can be described as follows according to the type of MIMO technology. A case where one stream is transmitted via a plurality of antennas may be referred to as spatial diversity, and a case where a plurality of streams is transmitted via a plurality of antennas may be referred to as spatial multiplexing. A mix of spatial diversity and spatial multiplexing may also be configured.

Now, a description is given of Channel State Information (CSI) reporting. In the current LTE standard, MIMO transmission schemes are classified into open-loop MIMO operating without CSI and closed-loop MIMO operating based on CSI. In particular, according to the closed-loop MIMO system, each of the eNB and the UE can perform beamforming based on CSI to obtain multiplexing gains of MIMO antennas. To obtain CSI from the UE, the eNB allocates PUCCH or PUSCH to command the UE to feed back CSI of the downlink signal.

The CSI is divided into three types of information: rank Indicator (RI), Precoding Matrix Index (PMI), and Channel Quality Indicator (CQI).

First, RI refers to rank information of a channel as described above, indicating the number of streams that a UE can receive on the same frequency-time resource. Since RI is determined by long-term fading of the channel, RI is generally fed back at a longer period than PMI or CQI. Second, the PMI indicates a precoding matrix index of the eNB preferred by the UE based on a metric such as a signal to interference noise ratio (SINR) as a value reflecting spatial characteristics of a channel. Finally, the CQI indicates a reception SINR, which is generally available when the eNB uses the PMI, as a value representing the channel strength.

According to the present invention, an RS port is configured by applying a transmission precoder to an RS for channel measurement of an eNB or a UE, and the precoder is applied through a circular loop of a specific pattern according to a specific time-frequency resource element, i.e., a time-frequency resource bundling unit PRG' or a UL precoding resource block group (PRG), or is applied while changing the precoder to a random precoder. PRG' or UL precodes resource block groups (PRGs). In particular, the present invention may be applied to both DL RS and UL RS, and may be typically applied to DL CSI-RS and UL SRS. RS applied to open-loop MIMO transmission or semi-open-loop MIMO transmission may be used, and RS may also be used for closed-loop MIMO transmission.

Recently, UL precoding SRS or DL precoding CSI-RS to which beamforming is applied is being discussed, and an operation scheme in which a plurality of precoding RSs are configured and a UE or eNB selectively indicates a specific precoding RS is being considered. In particular, the precoded RS of the present invention relates to an RS having a purpose different from a demodulation reference signal (DM-RS) for signal demodulation, for example, a purpose for CSI/MCS configuration and scheduling.

Applying the concept of time-frequency resource bundling to the precoded RS proposed in the present invention allows the receiving end to assume that the same precoder is used within the bundled resources, but may not assume that the same precoder is used between the bundled resources. Such a bundling resource unit (hereinafter, referred to as PRG') may be configured separately from a bundling resource unit (i.e., PRG) of the DM-RS used in the demodulation process, thereby improving flexibility of system operation, or may be restricted as in the conventional PRG, thereby simplifying system operation.

Alternatively, considering that the precoded RSs have a lower density than the DM-RSs, the bundled resource elements may be set to a multiple of the PRG, thereby improving channel measurement performance. Instead, the configuration may be restricted such that the multiple of the bundled resource units is the PRG.

Alternatively, the PRG' may be determined based on the transmission bandwidth of the SRS, i.e., the number of RBs. For example, the size of PRG' may be reduced as the bandwidth narrows to maintain the number of cyclic beams applied to SRS. If SRS hopping is configured, PRG' may be determined according to the transmission bandwidth or the number of RBs per hopping instance. Alternatively, even if SRS hopping is defined/configured, PRG 'may be determined based on the total corresponding SRS transmission band (i.e., the number of RBs allocated for SRS transmission), and in each hopping instance PRG' may be configured to determine and transmit precoders based on bundled resource elements of the bandwidth for the corresponding timing.

In the present invention, although the open-loop MIMO/semi-open-loop MIMO scheme is described under the assumption that beam circulation in which beams are changed in a specific time-frequency resource unit is basically performed, the proposal of the present invention can be applied to random open-loop/semi-open-loop MIMO transmission instead of beam circulation. The beam cycling refers to applying the PMI existing in a specific PMI set by cyclically changing the PMI as time-frequency resources vary. When there are a large number of time-frequency resources, all PMIs are applied, and then the PMIs are cyclically applied again starting from the first PMI in the PMI set. Alternatively, the PMI set may not be configured, and the PMI may be applied while randomly changing the PMI as time-frequency resources vary.

< first embodiment >

In a first embodiment of the present invention, a precoded SRS usage method is described, in which different precoders are configured in the PRG 'unit, i.e., the same precoder is applied within the PRG' resources.

1) First, a UL open loop/semi-open loop MIMO scheme will now be used, which uses UL precoded SRS.

By applying precoder bundling of the above PRG' units to SRS, the eNB may implicitly indicate to the UE the precoder or beam-cycling pattern for UL open-loop/semi-open-loop MIMO. For example, the UE is configured with N (precoded) SRSs (or SRS resources), and applies a different beam-cycling pattern or (semi-) open-loop MIMO scheme to each SRS (or SRS resource), and then transmits the SRS.

The UE transmits the precoded SRS through beam cycling in the PRG' unit, and transmits a plurality of precoded SRSs. A different beam cycling is applied for each precoded SRS. The eNB checks reception channels of the plurality of precoded SRSs, selects the best SRS, and notifies the UE of the selected SRS through the DCI. The eNB performs channel estimation in the PRG 'unit and selects an SRS (or SRS resource) having the best channel measurement quality based on an effective channel to which both the channel and the precoder are applied, although it is not known which precoder is applied to each PRG'. Then, the eNB indicates the selected SRS (or SRS resource) through the DCI. Next, the UE performs UL data transmission using a precoder applied to the SRS indicated by the DCI.

For example, when using SRS1 and SRS2 (or SRS resource 1 and SRS resource 2), the UE cyclically applies PMI 1 to PMI4 to SRS1 in the PRG 'unit, cyclically applies PMI5 to PMI8 to SRS2 in the PRG' unit, and then transmits the SRS. Next, when the eNB indicates the SRS1 through DCI (i.e., UL grant), the UE transmits data by cyclically applying PMI 1 to PMI4 applied to the SRS1 in a PRG unit, which is a bundling unit of the DM-RS. The UE divides the scheduled RBs in the PRG unit and cyclically applies PMIs 1 to 4 in the PRG unit. Then, the UE transmits the data and the DM-RS.

Further, the UE may autonomously determine a beam cycling pattern to be applied to each SRS. Alternatively, the eNB may specify the beam cycling pattern or assist the UE to autonomously determine the beam cycling pattern.

First, when a UE autonomously determines a precoder or beam-cycling pattern of (semi-) open-loop MIMO, the UE estimates a UL RS from the DL RS using DL/UL reciprocity, and autonomously determines a beam-cycling pattern/precoder. For example, in a dual codebook structure including codebooks W1 and W2, a UE selects N optimal codebooks W1 and performs beam-cycling or (semi) open-loop MIMO by applying different optimal codebooks W1 to N corresponding SRSs. That is, an independent codebook W1 is configured for each SRS, and the cyclic pattern of the codebook W2 is identically configured for all the SRS. As a result, independent cyclic beams can be applied to each SRS.

Alternatively, a precoder using common W1 may be configured for the SRS, but different precoders may be configured for the respective SRS by differently configuring W2. In this case, one of the beam selector section and the in-phase section constituting W2 may be differently configured for each SRS, and the other of the beam selector section and the in-phase section constituting W2 may be equally configured for each SRS. However, since the in-phase portion has a stronger tendency to be random, it is desirable to configure only the beam selector portion differently.

Even in an environment where DL/UL reciprocity is not available, the UE applies beam-cycling or (semi-) open-loop MIMO to N SRS in different directions. For example, the beam applied to each SRS is configured to cover a different 360/N degree direction in the vertical domain. Specifically, when there are 4 SRSs, the directions of precoders applied to the respective SRSs are configured to cover 0 to 90 degrees, 90 to 180 degrees, 180 to 270 degrees, and 270 to 360 degrees with respect to the respective SRSs.

If the eNB indicates the beam cycling mode, the eNB indicates Codebook Subset Restriction (CSR) to be used for each SRS, and the UE applies beam cycling or (semi-) open loop MIMO using restricted PMI to the CSR for each SRS. Alternatively, the eNB specifies W1 to be used for each SRS. When performing beam-cycling/half-open-loop MIMO for each SRS, the UE uses the designated W1 and generates beam cycling by cycling W2, or performs half-open-loop MIMO using the designated W1.

When the eNB helps the UE autonomously determine beam cycling (or open-loop/semi-open-loop MIMO), the eNB may restrictively specify one or more precoders that the UE should use for beam cycling (or open-loop/semi-open-loop MIMO) among all precoders in the codebook. The UE may freely determine beams within the restricted PMI set to perform beam cycling (or semi-open loop MIMO). The restriction of the precoder may be differently configured for each SRS, and a different PMI may be applied to each SRS to transmit. As an alternative approach, simply, precoder set restriction, or CSR, may be applied to each SRS in common. In this case, the UE performs semi-open loop or beam cycling using a different precoder for each SRS.

Further, the eNB may notify the UE of the number of layers that the UE should transmit, i.e., rank information, in addition to the SRS selection information. If the selected SRS is configured by N ports and M ranks are indicated, the condition that N ≧ M should be satisfied, and precoders applied to first to Mth ports of the N ports are used for transmission by mapping the precoders to the first to Mth layers in a one-to-one correspondence.

Alternatively, the eNB may notify only SRS selection information and not rank information to the UE. For example, SRS resource 1 to SRS resource 4 are configured, SRS resource 1 is configured by one port, SRS resource 2 is configured by two ports, SRS resource 3 is configured by 3 ports, and SRS resource 4 is configured by 4 ports. Therefore, if the eNB selects the SRS resource, the rank is automatically determined by the number of ports of the SRS. That is, if the SRS2 is selected and indicated, the eNB and the UE operate to transmit the PUSCH with rank 2 corresponding to the number of ports of the SRS 2.

2) A closed loop MIMO scheme using UL precoded SRS will now be described.

When using the UL closed-loop MIMO scheme, the eNB needs to indicate to the UE through DCI which precoder should be used to transmit UL data. When the eNB allocates frequency selective scheduling (i.e., a plurality of RBs) to one UE and indicates each PMI that should be used in a subband unit, the DCI payload size increases. This control channel overhead is reduced if UL precoded SRS is used.

The UE transmits UL SRS using different precoders in the PRG' unit. As described above, the eNB may restrict precoders to be used by the UE through CSR, or the eNB may pre-indicate W1, and the UE may freely select and apply W2. Alternatively, the UE may autonomously determine the precoder. Next, the UE performs beam cycling in the PRG' unit and transmits the SRS by applying a different beam.

The eNB measures a channel in the PRG 'unit after receiving the SRS, and indicates, to the UE, information on PRG' to which a precoder that the UE should use to transmit UL data is applied through DCI.

Specifically, the eNB indicates a specific PRG 'resource, and the UE transmits data using a precoder that has been used for SRS transmission on the indicated PRG' resource. If multiple SRSs are configured for the UE, the eNB indicates a specific SRS by an SRS indicator (SRI) and also indicates PRG' resources. The indication of PRG' resources may occupy a large DCI payload if the resources are wideband. Thus, the eNB should know the newly started resource unit after the beam cycle of the UE ends, and this information may be indicated to the UE by the eNB or may be reported to the eNB by the UE to share it.

For example, in the 20-RB system, when a PMI of PRG '1 RB and PMI of PMI {1, 2,3, 4} is sequentially applied through a circular loop, the eNB and the UE share information indicating that a resource element in which the PMI is cyclically applied once is 4PRG' (i.e., 4 RB). In this case, since the eNB recognizes that the same PMI has been applied to RB0, RB4, RB8, RB12, and RB16, if the eNB prefers the corresponding PMI, the eNB indicates RB0 that is a representative RB (e.g., the RB having the lowest index). Thus, since the eNB only needs to indicate one of RB0 through RB3, information may be transmitted using a total of 2-bit payload.

Alternatively, the concept of child resources may be introduced to perform the same operations. That is, a frequency band in which one SRS is transmitted is divided into a plurality of sub-resources, and a precoded SRS to which a different PMI is applied is transmitted on each sub-resource. Specifically, there are sub-resource 1 to sub-resource 4, and sub-resource 1 is configured as RB0, RB4, RB8, RB12, and RB 16. Sub-resource 2 is configured as RB1, RB5, RB9, RB13, and RB17, and sub-resource 3 is configured as RB2, RB6, RB10, RB14, and RB 18. Finally, sub-resource 4 is configured as RB3, RB7, RB11, RB15, and RB 19. In this case, the RBs constituting each sub-resource are uniformly distributed over all the resources, and the sub-resources are combined in a comb type to constitute all the resources. The eNB indicates the sub-resources through a 2-bit sized field and informs the UE which PMI should be used for data transmission.

As an alternative specific method, the eNB indicates scheduling information (resource allocation) through DCI after receiving the SRS. When transmitting data on the corresponding scheduling resources, the UE uses the precoder that has been used for SRS transmission on the scheduling resources. That is, the PMI for data transmission may be implicitly determined only by resource allocation information in the DCI, without additional information on the PMI.

< second embodiment >

In a second embodiment of the present invention, a precoded SRS using method is described, in which different precoders are configured in antenna port units, i.e., different precoders are applied to each antenna port.

(A) First, a case of applying the UL open loop/half open loop MIMO scheme will now be described.

If the beam circulation of the RS is applied, the density of the RS is reduced and the accuracy of channel measurement may be reduced. That is, the SRS and the CSI-RS are generally transmitted in all frequency bands, and when a precoder is changed in a PRG 'unit, an effective channel is randomly changed between PRB' resources, so that the accuracy of channel measurement is degraded.

Accordingly, beam cycling may not be applied to resources on which the SRS is transmitted and may be applied to SRS ports. For example, when SRS port 1 to SRS port 4 are configured, PMI is applied to each port in the order of PMI 1 to PMI 4. The UE transmits a plurality of SRSs to which different PMIs are applied, and the eNB selects the best SRS and indicates the selected SRS to the UE.

The eNB recognizes that a different PMI has been applied to each port of each SRS, and selects an optimal SRS when receiving data while cycling SRS ports in the PRG unit. For example, when it is assumed that UL data of rank 1 is transmitted, the eNB estimates channels h1 to h4 of SRS port 1 to SRS port 4 for the 4-port SRS1, and performs scheduling under the assumption that data is received while changing the channel estimated in the PRG unit. That is, the eNB determines MCS and resource allocation when receiving data on the assumption that channels h1, h2, h3, h4, h1 … are applied to PRG1, PRG2, PRG3, PRG4, PRG5 …, respectively.

In rank 2, it is assumed that two layers are transmitted through two SRS ports in each PRG. Both eNB and UE should know the two SRS ports to be assumed in each PRG. For example, assume that, for PRG1, PRG2, PRG3, PRG4, PRG5 …, data are transmitted through cascade channels [ h1 h2], [ h3 h4], [ h1 h4], [ h1 h2], [ h1 h2] …, respectively. In addition, it is assumed that the first layer is transmitted through a first channel vector of the concatenated channel and the second layer is transmitted through a second channel vector of the concatenated channel.

Since the eNB and the UE share the port cycle mode for the rank, if the eNB notifies the UE of rank information together with the SRI through DCI, i.e., UL grant, the UE may determine the beam cycle mode based on the corresponding port cycle mode. For example, when SRI is 1 and rank is 1, the UE transmits data by cycling precoders 1 to 4 that have been used by the UE through each port of SRS1(4 ports). That is, the UE transmits data and DM-RS by cyclically applying the precoders 1 to 4 in the PRG unit.

(B) Next, a case where the UL closed loop MIMO scheme is applied will be described.

The eNB may indicate an SRS port (along with SRI if multiple SRS are configured) instead of PMI for closed loop MIMO, and the UE may transmit data using a beam/PMI applied to the port. The plurality of ports constituting one SRS may be Code Division Multiplexed (CDM) or Frequency Division Multiplexed (FDM).

For example, when a plurality of ports are frequency division multiplexed, ports 1 to 4 in the 4-port SRS are cyclic frequency division multiplexed to PRG '(or specific resource unit) 1 to PRG' (or specific resource unit) 4, and the ports starting from port 1 are again frequency division multiplexed to PRG 'starting from PRG'5 by cyclic mapping. Alternatively, in the 8-port SRS, the (1,2), (3,4), (5,6) and (7,8) ports are cyclic frequency division multiplexed to PRG '(or a specific resource unit) 1 to PRG' (or a specific resource unit) 4, and the ports starting from the port (1,2) are frequency division multiplexed to PRG 'starting from PRG'5 by cyclic mapping. In this case, since the precoder is differently applied in the PRG' unit, the same effect as that of the first embodiment occurs, and the UE and the eNB can be operated similarly to the first embodiment.

< third embodiment >

In a third embodiment of the present invention, a precoded SRS usage method is described, wherein a different precoder is configured for each SRS resource.

In the first embodiment, a method of transmitting a precoder while changing a precoder in a PRG' unit on one SRS (or SRS resource) is described. However, the same operation can be performed by configuring a plurality of SRSs (or SRS resources) without introducing PRG'.

For example, in the first embodiment, PMI {1, 2,3, 4} circulates in a PRG' unit, whereas in the third embodiment, four SRSs are used, and the SRSs 1 to 4 are precoded to PMI 1 to PMI 4. However, SRS1 is transmitted on PRG '

resources

0, 4, 8, 12 …, SRS2 is transmitted on PRG'

resources

1, 5, 9, 13 …, SRS3 is transmitted on PRG '

resources

2, 6, 10, 14 …, and SRS4 is transmitted on PRG'

resources

3, 7, 11, 15 …, so that four SRSs are used as one SRS in the first embodiment. In this case, the eNB and the UE should recognize that the SRS1 to the SRS4 are one SRS group, and each SRS group has a different beam-cycling pattern. For example, SRS group 1 and SRS group 2 are configured, and each SRS group includes four SRSs. When the data transmission side circulates precoders for the SRSs belonging to the SRS group or transmits data by performing the circulation using the precoders, the eNB or the UE instructs or feeds back one SRS group to feed back CSI.

< fourth embodiment >

If a plurality of antenna panels are installed at the transmitting end, the channel status of each panel may be different. For example, multiple antenna panels may be installed in the antennas of the eNB. In this case, when a DL (semi) open loop MIMO transmission scheme is used, the UE may feed back information indicating that the UE desires to transmit DL data to the eNB through a specific panel. A particular panel may be limited to one with the best reception quality. In this case, the UE may also feed back CSI (i.e., RI, CQI, or a part of PMI such as W1) on the assumption that transmission using a (semi) open loop MIMO scheme is performed on the DL channel of the panel. Then, the eNB performs open-loop MIMO transmission on the corresponding panel.

Alternatively, a particular panel may indicate two or more subsets of all panels. In this case, the UE feeds back CSI (i.e., RI, CQI or a part of PMI such as W1) on the assumption that transmission using a (semi) open loop MIMO scheme is performed on the DL channel of the panel. That is, the UE calculates CSI while cycling through the panels in certain time-frequency resource elements. For example, when panel 1 and panel 2 are selected, the UE calculates CSI while alternating using panel 1 on RB0, using panel 2 on RB1, and using panel 1 again on RB 2. In transmitting DL data, the eNB transmits data while cycling the panel RB by RB in the same manner as the method for CSI calculation. That is, the eNB performs open loop MIMO transmission through a panel cycle. The feedback information may be panel selection information within a codebook if panel selection is performed within the codebook.

Even on the UL, the eNB notifies the UE (or the UE notifies the eNB) of information about a panel to be used for UL data transmission. Even during SRS transmission, the UE transmits the SRS while cycling the panel in each time-frequency resource element, and the eNB measures a channel and determines the MCS according to the SRS.

< fifth embodiment >

The eNB may indicate a portion of the CSI-RS ports to the UE, and the UE feeds back CSI using only the portion of the ports. For example, the eNB indicates 4 specific ports corresponding to a subset of 8-port CSI-RSs to the UE, and the UE calculates and feeds back CSI when transmitting data through semi-open loop MIMO for the 4 ports.

Alternatively, all ports are divided into disjoint partial ports and semi-open loop transmission is performed for the respective partial ports. In this case, each port group is used for transmission by cycling through specific time-frequency resource elements. For example, the 8-port CSI-RS is divided into 4 2-port groups and then used for data transmission by cycling through 2 ports and 2 ports in the RB unit. That is, port (0,1), port (2,3), port (4,5), port (6,7), port (0,1), … are cyclically used for RB1, RB2, RB3, RB4, RB5 …. During CSI calculation, the UE should also calculate CSI under the assumption that the port group is cycled.

< sixth embodiment >

The first to third embodiments have described a method of supporting open-loop MIMO or closed-loop MIMO transmission by diversifying a digital precoder through an RS. In the sixth embodiment, an application example of the present invention is described in terms of beam management.

For example, in the first embodiment, when different analog beams are circulated in a PRG ' unit for transmission on a per UL/DL beam management RS (hereinafter referred to as BRS and may be DL CSI-RS or UL SRS), the eNB may select PRG ' resources and indicate the selected resources to the UE to indicate that the UE should use the (analog) beam that has been used in the corresponding PRG ' of the corresponding BRS. The eNB may also provide BRS indication information if multiple BRSs are configured.

If the UL BRS is an SRS, the eNB indicates the SRS and the PRG' or one or a portion of the plurality of beams applied to the indicated SRS, and the UE uses the corresponding beam as a transmission beam.

If the DL BRS is a CSI-RS, the UE indicates the CSI-RS and the PRG' or one or a part of a plurality of beams applied to the indicated CSI-RS, and the eNB uses the corresponding beam as a transmission beam. Alternatively, in the PRG 'unit, one beam is applied to the DL CSI-RS without applying a different precoder, and the UE receives the DL CSI-RS by applying the reception beam differently in the PRG' unit. The UE selects a reception beam having good channel quality among a plurality of Rx beams configured in the PRG' unit and uses the selected beam as the reception beam when receiving DL data (or PDCCH).

Alternatively, the UE selects PRG 'resources and feeds back the selected resources to the eNB to indicate that the UE prefers the (analog) beam of the respective PRG' already used for the respective BRS. The UE may also provide BRS indication information if multiple BRSs are configured.

Unlike precoder indication information in terms of UL precoding, this beam indication information may not be indicated together with UL grant and may be transmitted together with DL grant, or a method of transmitting beam indication information together with DL grant or transmitting beam indication information through a dedicated DCI format or a dedicated RNTI may be used. The beam report information may be transmitted as a separate report from the CSI report. The beam report information may not be transmitted together with the CQI and/or RI, but may be transmitted together with Reference Signal Received Power (RSRP) corresponding to layer 1. Unlike DL/UL precoder indication, since a reception/transmission beam of a UE can be maintained for a long time, a method of indicating or reporting information using L2/L3 layer messages needs to be considered.

Referring to fig. 8, in step 801, a UE transmits to an eNB a plurality of precoded RSs to which a precoder cycling pattern is applied in predetermined resource elements, i.e., PRG' elements. Here, the precoder cycling pattern applied to the plurality of precoded RSs is defined as a combination of a first precoder for each of the plurality of precoded reference signals and a second precoder that is commonly applied to the plurality of precoded reference signals and cyclically applied in predetermined resource units. In particular, in a TDD system, a first precoder for each of a plurality of precoded RSs may be determined using DL RSs received from an eNB.

More desirably, the precoder cycling pattern applied to the plurality of precoded RSs precodes the precoded RSs in different directions in the horizontal domain, and can be defined to cover all horizontal directions.

Next, in step 803, the UE receives information indicating one of the plurality of precoded RSs from the eNB, and in step 805, the UE transmits the UL data signal and UL DM-RS using a precoder cycling pattern applied to the indicated precoded RS.

In addition, the UE may receive information on the predetermined resource unit from the eNB in advance.

Fig. 9 shows a BS and a UE suitable for use in embodiments of the present invention.

Referring to fig. 9, the wireless communication system includes a BS 110 and a UE 120. BS 110 includes a processor 112, a memory 114, and a Radio Frequency (RF) unit 116. The processor 112 may be configured to implement the processes and/or methods set forth in the present invention. The memory 114 is connected to the processor 112 and stores various information related to the operation of the processor 112. The RF unit 116 is connected to the processor 112 and transmits and/or receives a radio signal. UE 120 includes a processor 122, a memory 124, and an RF unit 126. The processor 122 may be configured to implement the processes and/or methods set forth in the present invention. The memory 124 is connected to the processor 122 and stores various information related to the operation of the processor 122. The RF unit 126 is connected to the processor 122 and transmits and/or receives a radio signal. BS 110 and/or UE 120 may have a single antenna or multiple antennas.

The above-described embodiments correspond to combinations of elements and features of the present invention in the prescribed forms. Also, it can be considered that the respective elements or features are optional unless they are explicitly mentioned. Each element or feature may be implemented in a form that cannot be combined with other elements or features. Further, the embodiments of the present invention can be realized by partially combining elements and/or features together. The order of operations explained for each embodiment of the present invention may be modified. Some configurations or features of one embodiment may be included in another embodiment or may replace corresponding configurations or features of another embodiment. Also, it is obviously understood that the embodiments are constituted by combining claims which are not explicitly cited in the appended claims, or may be included as new claims by amendment after the application is filed.

In the present disclosure, in some cases, a specific operation explained as being performed by a base station may be performed by an upper node of the base station. In particular, in a network configured by a plurality of network nodes including a base station, it is apparent that various operations performed for communication with a terminal may be performed by the base station or other networks other than the base station. "Base Station (BS)" may be replaced with terms such as fixed station, Node B, eNode B (eNB), Access Point (AP), and the like.

Embodiments of the present invention may be implemented in various ways. For example, embodiments of the invention may be implemented using hardware, firmware, software, and/or any combination thereof. In the case of being implemented by hardware, the method according to each embodiment of the present invention may be implemented by at least one of an ASIC (application specific integrated circuit), a DSP (digital signal processor), a DSPD (digital signal processing device), a PLD (programmable logic device), an FPGA (field programmable gate array), a processor, a controller, a microcontroller, a microprocessor, and the like.

In the case of implementation by firmware or software, the method according to each embodiment of the present invention may be implemented by a module, a procedure, and/or functions for performing the above-described functions or operations. The software codes are stored in memory units and may then be driven by processors. The memory unit is provided inside or outside the processor to exchange data with the processor through various means known in the public.

The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

It will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. The detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[ Industrial Applicability ]

Although the above-described method of applying a resource bundling-based precoder in a wireless communication system and apparatus thereof have been described focusing on an example applied to a 3gpp lte system, the present invention is applicable to various wireless communication systems other than the 3gpp lte system.

Claims

1. A method of transmitting an uplink signal by a user equipment, UE, in a wireless communication system, the method comprising:

receiving information on SRS resource elements among predetermined sounding reference signal SRS resource elements from a base station BS,

wherein each of the predetermined SRS resource elements corresponds to a different analog beam;

transmitting a plurality of precoded SRSs to which a precoder cycling pattern is applied for each of the SRS resource elements to the BS,

wherein the plurality of precoded SRSs are transmitted with each of the reference signal received powers, RSRPs, corresponding to the plurality of precoded SRSs, and the plurality of precoded SRSs are not transmitted with a channel quality indicator, CQI, and a rank indicator, RI;

receiving information on a transmission analog beam and a reception analog beam from the BS through a Downlink Control Information (DCI) format other than a DCI format for an uplink grant and a downlink grant;

receiving information indicating one of the plurality of precoded SRSs from the BS through a DCI format for an uplink grant based on the information on the transmit analog beam and the receive analog beam; and

transmitting an uplink data signal and an uplink demodulation reference signal to the BS based on the uplink grant and based on a precoder cycling pattern applied to the indicated precoded SRS.

2. The method of claim 1, wherein the precoder cycling pattern applied to the plurality of precoded SRSs is defined as a combination of a first precoder for each of the plurality of precoded SRSs and a second precoder applied in common to the plurality of precoded SRSs, the second precoder being cyclically applied for each of the SRS resource elements.

3. The method of claim 2, further comprising:

receiving a downlink reference signal from the BS; and

determining the first precoder for each of the plurality of precoded SRSs based on the downlink reference signal.

4. The method of claim 1, wherein the precoder cycling pattern applied to the plurality of precoded SRSs precodes the precoded SRSs in a horizontal domain and is defined to cover all horizontal directions.

5. A user equipment, UE, in a wireless communication system, the UE comprising:

a wireless communication module; and

a processor connected to the wireless communication module and configured to:

6. The UE of claim 5, wherein the precoder cycling pattern applied to the plurality of precoded SRSs is defined as a combination of a first precoder for each of the plurality of precoded SRSs and a second precoder applied in common to the plurality of precoded SRSs, the second precoder being cyclically applied for each of the SRS resource elements.

7. The UE of claim 6, wherein the processor is further configured to:

receiving a downlink reference signal from the BS; and

determining the first precoder for each of the plurality of precoded SRSs based on the downlink reference signal received from the BS.

8. The UE of claim 5, wherein the precoder cycling pattern applied to the plurality of precoded SRSs precodes the precoded SRSs in a horizontal domain and is defined to cover all horizontal directions.